Multiple Key Event Bindings in Tkinter - “Control + E” “Command (apple) + E” etc

Question

Mac OS X 10.6.6 - Tkinter

I want to bind multiple-key events, and while I have found an effbot article and the Tk man pages, I\'ve been unable to make this work corr

Answer 1

Option 1

Something like this:

# Status of control, shift and control+shift keys in Python
import tkinter as tk

ctrl = False
shift = False
ctrl_shift = False

def key(event):
    global ctrl, shift, ctrl_shift
    #print(event.keycode, event.keysym, event.state)
    if ctrl_shift:
        print('<Ctrl>+<Shift>+{}'.format(event.keysym))
    elif ctrl:
        print('<Ctrl>+{}'.format(event.keysym))
    elif shift:
        print('<Shift>+{}'.format(event.keysym))
    ctrl = False
    shift = False
    ctrl_shift = False

def control_key(state, event=None):
    ''' Controll button is pressed or released '''
    global ctrl
    ctrl = state

def shift_key(state, event=None):
    ''' Controll button is pressed or released '''
    global shift
    shift = state
    control_shift(state)

def control_shift(state):
    ''' <Ctrl>+<Shift> buttons are pressed or released '''
    global ctrl, ctrl_shift
    if ctrl == True and state == True:
        ctrl_shift = True
    else:
        ctrl_shift = False

root = tk.Tk()
root.geometry('256x256+0+0')

root.event_add('<<ControlOn>>',  '<KeyPress-Control_L>',   '<KeyPress-Control_R>')
root.event_add('<<ControlOff>>', '<KeyRelease-Control_L>', '<KeyRelease-Control_R>')
root.event_add('<<ShiftOn>>',    '<KeyPress-Shift_L>',     '<KeyPress-Shift_R>')
root.event_add('<<ShiftOff>>',   '<KeyRelease-Shift_L>',   '<KeyRelease-Shift_R>')

root.bind('<<ControlOn>>', lambda e: control_key(True))
root.bind('<<ControlOff>>', lambda e: control_key(False))
root.bind('<<ShiftOn>>', lambda e: shift_key(True))
root.bind('<<ShiftOff>>', lambda e: shift_key(False))
root.bind('<Key>', key)

root.mainloop()

Option 2

However, in the end, I decided to process keystrokes manually. You can se the example in this file. First, I set keycodes and shortcuts in two dictionaries self.keycode and self.__shortcuts:

# List of shortcuts in the following format: [name, keycode, function]
self.keycode = {}  # init key codes
if os.name == 'nt':  # Windows OS
    self.keycode = {
        'o': 79,
        'w': 87,
        'r': 82,
        'q': 81,
        'h': 72,
        's': 83,
        'a': 65,
    }
else:  # Linux OS
    self.keycode = {
        'o': 32,
        'w': 25,
        'r': 27,
        'q': 24,
        'h': 43,
        's': 39,
        'a': 38,
     }
self.__shortcuts = [['Ctrl+O', self.keycode['o'], self.__open_image],   # 0 open image
                    ['Ctrl+W', self.keycode['w'], self.__close_image],  # 1 close image
                    ['Ctrl+R', self.keycode['r'], self.__roll],         # 2 rolling window
                    ['Ctrl+Q', self.keycode['q'], self.__toggle_poly],  # 3 toggle between roi/hole drawing
                    ['Ctrl+H', self.keycode['h'], self.__open_poly],    # 4 open polygons for the image
                    ['Ctrl+S', self.keycode['s'], self.__save_poly],    # 5 save polygons of the image
                    ['Ctrl+A', self.keycode['a'], self.__show_rect]]    # 6 show rolling window rectangle

Then added self.__keystroke function to monitor <Ctrl> keystroke events. This function checks if <Ctrl> key is pressed or not:

def __keystroke(self, event):
    """ Language independent handle events from the keyboard """
    #print(event.keycode, event.keysym, event.state)  # uncomment it for debug purposes
    if event.state - self.__previous_state == 4:  # check if <Control> key is pressed
        for shortcut in self.__shortcuts:
            if event.keycode == shortcut[1]:
                shortcut[2]()
    else:  # remember previous state of the event
        self.__previous_state = event.state

Finally, bind the self.__keystroke function to the master GUI window. Note that this function is bonded in the idle mode, because multiple keystrokes slow down the program on weak computers:

# Handle keystrokes in the idle mode, because program slows down on a weak computers,
# when too many key stroke events in the same time.
self.master.bind('<Key>', lambda event: self.master.after_idle(self.__keystroke, event))

Answer 2

With Tkinter, "Control-R" means Ctrl-Shift-R whereas "Control-r" means Ctrl-R. So make sure you're not mixing up uppercase and lowercase.

Answer 3

This appears to be a bug in Tk. I get the same error with tcl/tk on the mac as well as with python/tkinter. You can bind <Command-e> to a widget (I tried with a text widget) but binding it to the root window or to "all" seems to cause the error you get.

Answer 4

Enhanced to cover the Alt and Meta keys, aka Option and Command on macOS.

# Original <https://StackOverflow.com/questions/6378556/
#           multiple-key-event-bindings-in-tkinter-control-e-command-apple-e-etc>

# Status of alt (ak option), control, meta (aka command)
# and shift keys in Python tkinter

# Note, tested only on macOS 10.13.6 with Python 3.7.4 and Tk 8.6.9

import tkinter as tk
import sys

_macOS = sys.platform == 'darwin'
_Alt   = 'Option' if _macOS else 'Alt'
_Ctrl  = 'Control'
_Meta  = 'Command' if _macOS else 'Meta'
_Shift = 'Shift'

alt = ctrl = meta = shift = ''


def up_down(mod, down):
    print('<%s> %s' % (mod, 'down' if down else 'up'))
    return down


def key(event):
    '''Other key pressed or released'''
    # print(event.keycode, event.keysym, event.down)
    global alt, ctrl, meta, shift
    t = [m for m in (alt, ctrl, shift, meta, str(event.keysym)) if m]
    print('+'.join(t))


def alt_key(down, *unused):
    '''Alt (aka Option on macOS) key is pressed or released'''
    global alt
    alt = up_down(_Alt, down)


def control_key(down, *unused):
    '''Control key is pressed or released'''
    global ctrl
    ctrl = up_down(_Ctrl, down)


def meta_key(down, *unused):
    '''Meta (aka Command on macOS) key is pressed or released'''
    global meta
    meta = up_down(_Meta, down)


def shift_key(down, *unused):
    '''Shift button is pressed or released'''
    global shift
    shift = up_down(_Shift, down)


def modifier(root, mod, handler, down):
    '''Add events and handlers for key press and release'''
    root.event_add('<<%sOn>>' % (mod,), ' <KeyPress-%s_L>' % (mod,), '<KeyPress-%s_R>' % (mod,))
    root.bind(     '<<%sOn>>' % (mod,), lambda _: handler('<%s>' % (down,)))

    root.event_add('<<%sOff>>' % (mod,), '<KeyRelease-%s_L>' % (mod,), '<KeyRelease-%s_R>' % (mod,))
    root.bind(     '<<%sOff>>' % (mod,), lambda _: handler(''))


root = tk.Tk()
root.geometry('256x64+0+0')

modifier(root, 'Alt',     alt_key,     _Alt)
modifier(root, 'Control', control_key, _Ctrl)
modifier(root, 'Meta',    meta_key,    _Meta)
modifier(root, 'Shift',   shift_key,   _Shift)

root.bind('<Key>', key)

root.mainloop()